The present invention relates to the field of torch cutting and welding metallic objects underwater by means of an electric arc established between an electrode and the metallic object. Such metallic objects can be underwater portions of ships and the like, fixed submerged structures such as bridge pillings and especially underwater portions of offshore oil and gas drilling platforms.
The most frequently utilized electric-arc cutting process underwater is the oxygen arc process wherein an electric arc is struck between an electrode and the workpiece. Simultaneously a stream of oxygen gas is blown into the arc. This cutting process is inaccurate and results in a rough cutting trace. The oxygen gas bubbles reduce the sight of the operator and further the use of oxygen increases the safety hazards.
U.S. Pat. No. 4,842,154 discloses a disc arc cutting apparatus wherein an arc is generated between the periphery of the disc and the workpiece. The rotating disc is moved along the workpiece which will melt and the rotational movement of the disc will remove melted material from the workpiece. The main problem with this technique is related to the safety hazards of the rotating disc. With the disc arc cutting process it is not possible to obtain holes and the like in the workpiece.